[librsvg] (9 commits) ...Merge branch 'log-nonexistent-references' into 'master'

[Federico Mena Quintero <federico src gnome org>]

Summary of changes:

  0e16507... (#368): Log when an element is not rendered due to a nonexi
  ea14943... NodeTRef: log if the referenced element is nonexistent
  b5d87c6... marker.rs: Log when a referenced marker is not found
  aaf92eb... DrawingCtx: log when an element references a nonexistent ma
  4df9821... gradient.rs: Log when referencing a nonexistent gradient
  39e9434... paint_server.rs: Log when there is a nonexistent pattern wi
  033da1d... NodeUse: Log when referencing a nonexistent element
  a554502... pattern.rs: Log when we find a circular reference
  2ba147a... Merge branch 'log-nonexistent-references' into 'master'